Sorry to hear IBS made you late of work!! It is very typical of IBS, you need to run to the bathroom usually the first thing in the morning. It's really annoying!
If you have the diarrhoea type, then insoluble fibre won't help you. First you need to get rid of all irritants such as coffee, too much alcohol, carbonated drinks, fatty and sugary foods. Sugar and artificial swweteners alone cause diarrhoea for many... not to mention coffee. You may want to limit your coffee intake if you don't want to give it up. That's what I did. Also fatty foods are bad. Irritants are often individualized, so it'll take some time for you to find them out. But it is well worth it.
Some people may eat too much fibre, but I don't know how common that is because generally people don't eat very healthy. But if you think this might apply to you, maybe you can cut down on fibre. You might also like to find out the difference between soluble fibre and insoluble fibre.
I hope this helps. Good luck.